Mineral acid inhibitor



3,047,511 Patented July 31, 1962 This invention relates to a corrosion inhibitor for use in aqueous, non-oxidizing acids to inhibit the corrosion of ferrous based metals and nickel by such acids. It more particularly relates to the use of 3-butyn-2-one as a corrosion inhibitor for use in such acids.

In practicing this invention, 3-butyn-2-one HOgO-i'J-CHQ is dissolved in the aqueous acid, the corrosive action of which is to be inhibited. By aqueous acid is meant any composition comprising a non-oxidizing acid and water and does not mean to exclude the presence of other substances. Only a small amount of the inhibitor is needed in the aqueous acids, as little as a few thousandths of 1 percent, based on the weight of aqueous acid, significantly reducing the corrosion of iron, steel or nickel exposed to the acid. The degree of inhibition increases with the concentration of the inhibitor up to a level of about 1 percent. Beyond this point little added protection of the metal is obtained by the use of more inhibitor. Generally, it is preferred to use the inhibitor at al evel of about 0.1 to 0.4 percent of the total weight of acid, this amount being adequate for most purposes.

The 3-butyn-2-one is an etfective inhibitor not only at ordinary temperatures, but also at elevated temperatures up to the decomposition point of the compound. High effectiveness is shown at 150 Fahrenheit and higher. Moreover, it is effective as an inhibitor in various concentrations of acids; e.g., even in commercial concentrated hydrochloric acids containing up to 37 percent hydrogen chloride.

Applications in which the inhibitor is particularly useful include metal-picl 1ing, cleaning and polishing baths, oil well-acidizing solutions, boiler-cleaning compositions and the like.

The 3-butyn-2-one is easily made by the controlled electrolytic oxidation of the corresponding alkynol in acid solution according to the method reported by Wolf, Chem. Ber., 87, 668-76 (1954).

In order to demonstrate the effectiveness of the inhibitor 0.4 percent of the 3-butyn-2-one was put into a 10 percent aqueous solution of hydrochloric acid ml.) held at 150 F. and a coupon (2.75 in. x 1.0 in. x 0.12 in.) of AISI-l020 mild steel was suspended in the solution for 16 hrs. Thereafter the coupon was cleaned, dried and weighted to determine the amount of metal dissolved. Table I compares the result of this test with that obtained using a similar metal coupon in a non-inhibited 10 percent aqueous solution of hydrochloric acid.

TABLE I Corrosion of AISI-1020 Mild Steel by 10 Percent HCl in the Presence of 0.4 Percent 3-Butyn-2-One Concentration Concentration Soln. Corrosion Example No. 3-Butyn-2- Hydrochloric Tern Rate,

One (Percent) Acid (Percent) F.) lbJftfl/day 0.4 10 O. 077 (no inhibitor). 10 1 Results generally paralleling those shown in Table I were obtained when similar tsets were run at lower temperatures, with lower or higher concentration of HCl, or with other ferrous metals or nicket as the test metal. Likewise, other aqueous non-oxidizing acids, such as phosphoric, sulfuric and acetic aids are similary inhibited.

Various modifications can be made in the present invention without departing from the spirt or scope thereof for it is understood that I limit myself only as defined in the appended claims.

I claim:

1. An aqueous solution of a non-oxidizing acid containing an eifective amount of 3-butyn-2-one corrosion inhibitor.

2. An aqueous solution of a non-oxidizing acid containing from about 0.1 to about 1 percent of 3 butyn-2- one corrosion inhibitor.

References Cited in the file of this patent UNITED STATES PATENTS 2,106,181 Kreimeier Jan. 25, 1938 2,838,458 Baohtel June 10, 1958 2,905,588 Youngson Sept. 22, 1959 2,913,408 Pumpelly et-al Nov. 17, 1959 FOREIGN PATENTS 468,231 Italy Dec. 29, 1951 235,291 Switzerland Apr. 3, 1945 

1. AN AQUEOUS SOLUTION OF A NON-OXIDIZING ACID CONTAINING AN EFFECTIVE AMOUNT OF 3-BUTYN-2-ONE CORROSION INHIBITOR. 